Scientists at Cal Tech's Jet Propulsion Laboratory has discovered that the gigantic ice sheets of Greenland and Antarctica are melting much faster than anyone ever expected.

As a result, the seas could potentially rise much faster, as well, eventually causing coastal erosion, changes in surface water quality, and catastrophic flooding.

And while Greenland and Antarctica seem a hell of a long way from LA, the City of Angels is on a list of 21 “mega-cities” that are in direct peril due to rising oceans.

According to the recent study, which examined 18 years worth of data from NASA satellites – the longest to date looking at changes in the polar ice sheets – the Greenland and Antarctic ice sheets lost a combined mass of 475 gigatonnes a year on average.

The study also revealed that the two ice sheets lost an average of roughly 36 gigatonnes more than they did the year before. (A gigatonne is one billion metric tons, or more than 2.2 trillion pounds.)

The realization that the two polar ice sheets are dumping so much water into the oceans means that they are now the No. 1 contributor to rising sea levels, placing them ahead of melting mountain glaciers and ice caps much sooner than climate models have predicted.

“That ice sheets will dominate future sea level rise is not surprising — they hold a lot more ice mass than mountain glaciers,” lead author Eric Rignot of the Jet Propulsion Laboratory in Pasadena said in a statement. “What is surprising is this increased contribution by the ice sheets is already happening. If present trends continue, sea level is likely to be significantly higher than levels projected” by United Nations climate experts in 2007.

Rignot and his team conclude that if the two ice sheets continue to melt at this accelerated rate over the next 40 years, the seas could rise by about six inches. Added to the predicted rate of sea level rising caused by melting glacial ice caps and thermal expansion, the oceans could rise by as much as 12-plus inches.

While this latest news doesn't mean folks in LA should run out right away to buy Swimmies and a canoe, scientists say the inescapable truth that the seas are rising faster than anticipated will have a serious impact.

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